Overestimated global warming over the past 20 years

It’s three years old, but I don’t recall it at the time, and it’s still highly relevant:

Recent observed global warming is significantly less than that simulated by climate models. This difference might be explained by some combination of errors in external forcing, model response and internal climate variability.

Global mean surface temperature over the past 20 years (1993–2012) rose at a rate of 0.14 ± 0.06 °C per decade (95% confidence interval). This rate of warming is significantly slower than that simulated by the climate models participating in Phase 5 of the Coupled Model Intercomparison Project (CMIP5). To illustrate this, we considered trends in global mean surface temperature computed from 117 simulations of the climate by 37 CMIP5 models (see Supplementary Information).

These models generally simulate natural variability — including that associated with the El Niño–Southern Oscillation and explosive volcanic eruptions — as well as estimate the combined response of climate to changes in greenhouse gas concentrations, aerosol abundance (of sulphate, black carbon and organic carbon, for example), ozone concentrations (tropospheric and stratospheric), land use (for example, deforestation) and solar variability. By averaging simulated temperatures only at locations where corresponding observations exist, we find an average simulated rise in global mean surface temperature of 0.30 ± 0.02 °C per decade (using 95% confidence intervals on the model average).

The observed rate of warming given above is less than half of this simulated rate, and only a few simulations provide warming trends within the range of observational uncertainty (Fig. 1a).

The inconsistency between observed and simulated global warming is even more striking for temperature trends computed over the past fifteen years (1998–2012). For this period, the observed trend of 0.05 ± 0.08 °C per decade is more than four times smaller than the average simulated trend of 0.21 ± 0.03 °C per decade (Fig. 1b). It is worth noting that the observed trend over this period — not significantly different from zero — suggests a temporary ‘hiatus’ in global warming. The divergence between observed and CMIP5- simulated global warming begins in the early 1990s, as can be seen when comparing observed and simulated running trends from 1970–2012 (Fig. 2a and 2b for 20-year and 15-year running trends, respectively the current generation of climate models (when run as a group, with the CMIP5 prescribed forcings) do not reproduce the observed global warming over the last 20 years, or the slowdown in global warming over the past fifteen years. This interpretation is supported by statistical tests of the null hypothesis that the observed and model mean trends are equal, exchangeable with each other (that is, the ‘truth plus error’ view); or (2) the models are exchangeable with each other and with the observations (see Supplementary Information).

Differences between observed and simulated 20-year trends have p values (Supplementary Information) that drop to close to zero by 1993–2012 under assumption (1) and to 0.04 under
assumption (2) (Fig. 2c). Here we note that the smaller the p value is, the stronger the evidence against the null hypothesis. On this basis, the rarity of the 1993–2012 trend difference under assumption (1) is obvious. Under assumption (2), this implies that such an inconsistency is only expected to occur by chance once in 500 years, if 20-year periods are considered statistically independent. Similar results apply to trends for 1998–2012 (Fig. 2d). In conclusion, we reject the null hypothesis that the observed and model mean trends are equal at the 10% level.

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Recent Comments

Amber

One of the most significant outcomes of the USA election is the public awakening to the utter contempt main street media holds them . Preachy condescending Liberals
pushing for the most part Democrat ideology while shutting out different values and political priorities . Telling the people what to think instead of listening . The Green Party garnering a whopping 1 % of the vote and was supposed to be the champion of what the President claims is the number one threat to the world . Global Warming rebranded Climate Change . Apparently people in the rust belt and over 30 other States disagreed with that as a priority .
The lazy media played along and sold scary climate stories they were spoon fed and in some cases refused to provide any balance to the BS they are spoon fed and have been spewing for years .
When their party lost they were so stunned all they could play was the race card and are still in denial holding out for hopeless recounts or conspiracy theories of Russian espionage and hacking .
The public has now been put back in control so if some clown weather women wants to pitch nonsense the public shifts to more objective information sources. Ones that aren’t the propaganda or fake news tool for a political party .
Universities that are now full on incubators for a one sided left wing agenda are really ripping those kids off but worst of all those like Colorado University have faculty openly saying they will not discuss opposing climate views . Education to Propaganda is a fine line . Colorado crossed it . The LA times crossed it . The Guardian , New York Times …. well what do you expect ?
Peoples actions demonstrated the jig is up . Short those media stocks they are going down .

Amber

If left wing pinko Saunders doesn’t like him he sounds like he has potential .
He looks like a guy with a bit of backbone and won’t be bullied by the Demo rat
whiners who have infiltrated the EPA .
Good luck Mr. Pruitt . …. hire security . When the looney tunes get desperate( and they are ) they go into ugly mode . Taking apart their $Trillion dollar con game is going to get them down right belligerent but who cares ? They did get about 1 % of the vote
after all . In other words the science fiction is settled in the minds of voters by about
99 % . The debate is over in their hot air world .
Drain away Mr. Pruitt the public backs you despite the shrill sound of whiners who just had their piggy bank broken .

Amber

The NASA data manipulators collectively don’t have an IQ over 38 . Bullshit merchants about to be out on their ass . Maybe Britain would like to hire NASA rejects .
Where oh where are Dicaprio and Gore going to get their alarmist propaganda ?
When is the much vaunted IPCC report coming out ? That’s right NEVER .
The jig is up they were played as useful idiots and are no longer required .
Did the IPCC hot pants smut writer ever beat those sexual harassment allegations ? Quality right through the organization .

Amber

Why would virtually no change to Antarctic ice in over 100 years be a surprise at all .
Whether it’s minus – 60 or minus – 58 certainly we know it is fricking cold and it is not about to thaw . Throw a few volcanos open below the surface and a part of it might
but if that is considered caused by climate change the science fiction is bigger than
we know .
The question is how much will the Antarctic grow by over the next 1000 years ?

Amirlach

JayPee

I’m willing to consider your argument, but I’m disturbed of your willing to give credence to the unproven and unfoundedly assumed presumption that CO2, CH4, and any other gasses that the extremist left hates are upon their dictum alone the mythical GREENHOUSE GASSES as they define them to be.

I ask you not to buy into their argument without the proof that they have never had.
They have always had conjecture, lies and hysteria and even a low percentage of consensus ( as if that means anything ).
But they have NEVER had proof of their mythical GREENHOUSE EFFECT ( as defined by the extremist left ).